when my car is hot only intermittently it will start idling very lumpy then gets worse very quickly.and just cuts out.then if i try to drive it judders and backfires!it will start again straight away but will cut out unless i hold the revs up.when i do this the fuel pump speeds up and slows down and the revs go up and down.if i leave the car for a while then it as if the problem never happened!any help appreciated guys, cheers.

 

Check the voltage to the fuel pump but I suspect the pump is going fooked as this happened to my S1 once. The fuel pressure was all over the place.

 

will check it, cheers mate.the fuel pump is alsmost new and from a scorpio cosworth.